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364                         METALLURGY OF IRON AND STEEL.
centage cold-shortness rapidly increases. In amounts not exceeding .66 per cent., the tensile strength is raised considerably. It lowers the elastic limit, and decreases the elongation and reduction of area in a marked degree. It makes the steel harden more in quenching,, and injures its welding power even when only .093 per cent, is present.
These results have been corroborated by J. E. Stead,* who found that between .10 and .15 per cent, of arsenic in structural steel has no effect upon the mechanical properties; the tenacity is but slightly increased, the elongation and reduction of area unaffected. With .20 per cent, of arsenic, the difference is noticeable, while with larger amounts the effect is decisive. When one per cent, is present, the tenacity is increased, and the elongation and reduction of area both reduced. This increase in strength and diminution in toughness continue as the content of arsenic is raised to 4 per cent., when the elongation and reduction in area become nil. These experiments are of practical importance, since many steels carry an appreciable proportion of arsenic. Some chemists take little cognizance of this fact, and their phosphorus determinations are too high on account of the presence of arsenic in the phosphorus precipitate. Other analysts take special precautions to avoid this contamination.
SEC. XVIIi.—Influence of nickel, tungsten and chromium.— The first public presentation of the effect of nickel upon steel was a paper by Jas. Eiley.f Since that time the properties of nickel steel have become widely known. As often happens in the case of a new metal, the tendency is to exaggerate its importance. In a paper read before the American Society of Civil Engineers, in June, 1895, I gave the detailed results found by testing nickel steel when rolled into rounds, angles and plates, and compared them with the records of carbon steel of the same tensile strength. A condensation of the work will be found in Table XYII-L. The nickel steel is superior, but in less measure than may be generally supposed. It must -be -kept in mind, however, that in armor plate, as in many another field, there is sometimes but a very small distance between absolute success and absolute failure, and that it matters little how much margin there is above success, provided there is a margin at all.
* The Effect of Arsenic on Steel.   Journal I. and S, I., Vol. 1,1895, p. 77. t Alloys of Nickel and. Steel,  Journal I. and S. I., Vol. 1,1889, p. 45,